It is known that the suppression of the functions of bone marrow by various causes seriously worsens systemic conditions to pose peril to life. As morbidities due to such bone marrow suppression symptoms, hypoplastic anemia, thrombo-cytopenia, leukopenia and the like are known.
The mechanisms of the onset of leukopenia among them are classified into those involving a decrease in leukocyte production and those involving the acceleration of leukocyte destruction. Causes for the decrease in leukocyte production include congenital diseases, irradiation with radiation, hypoplastic anemia, administration of an antitumor agent or antibiotic, etc. On the other hand, causes for the acceleration of leukocyte destruction include infectious diseases, immunological abnormalities, etc.
As a therapeutic method for leukopenia, the administration of granulocyte colony-stimulating factor (G-CSF) or macrophage-colony stimulating factor is a promising means at present. On the other hand, erythropoietin is used for treating erythropenia. The application of interleukin-6, interleukin-11, thrombopoietin and the like as medicine is in progress for treating thrombocytopenia. In addition, the application of interleukin-3, granulocyte-macrophage-colony stimulating factor (GM-CSF) and the like as therapeutic agent for bone marrow suppression is in progress.
On the other hand, for example, compounds formed by the substitution of an N-acyl-N-alkylamino group at the 1-position of a sugar are known (JP-B-1-40036) as compounds having defensive effect on infectious diseases caused by bacteria, fungi, etc.
Sulphostin can be obtained by culturing a microorganism belonging to the genus Streptomyces and compounds analogous thereto can be obtained by chemical synthesis. Sulphostin and the analogous compounds thereto are hereinafter referred to as sulphostin-related compounds. These sulphostin-related compounds have an inhibitory effect on dipeptidyl peptidase IV and hence are expected as physiologically active substances such as, for example, an immunomodulator, a hormone modulator, an anti-HIV agent, an antiallergic agent, an anti-inflammatory agent and an antirheumatic agent WO 99/25719 and JP-A-2000-327689).